Heat sink assembly with heat pipe

ABSTRACT

A heat sink assembly with heat pipe includes at least one aluminum fin assembly and at least one copper heat pipe, which are made of dissimilar metal materials. The aluminum fin assembly includes at least one area to be connected to other members of the heat sink assembly, such as a groove. A copper embedding layer is provided on a groove inner surface of the groove for connecting the aluminum fin assembly to the copper heat pipe. By providing the copper embedding layer, the connection between the aluminum fin assembly and the copper heat pipe made of dissimilar metal materials is improved, and the problems of eutectic grains formed on the surface of the aluminum fin assembly and environmental pollution caused by electroless nickel plating are eliminated.

This application claims the priority benefit of Taiwan patent application number 111103914 filed on Jan. 28, 2022.

FIELD OF THE INVENTION

The present invention relates to a heat sink, and more particularly, to a heat sink assembly with heat pipe, which includes a copper embedding layer provided on areas of an aluminum fin assembly to be connected to other members of the heat sink assembly, so that the aluminum fin assembly can be directly connected with copper heat pipes via welding without the need of electroless nickel plating.

BACKGROUND OF THE INVENTION

Heat sinks or radiation fins are usually used with an electronic element or in a system to dissipate heat produced by the element or the system through heat exchange. In the case of having a relatively low thermal resistance, the radiation fins show relatively high heat dissipation efficiency. Generally, thermal resistance includes the thermal spreading resistance in the radiation fins and the convection thermal resistance between the radiation fin surface and the atmospheric environment. Currently, some more efficient heat dissipation systems use a combination of high-conductivity heat pipes and fins of heat sink to effectively solve the problem of heat dissipation.

Generally, a thermal module with heat pipe includes at least one heat pipe and a plurality of spacedly arranged fins, and any two adjacent fins together define a flow passage between them. The fins are respectively provided with a through hole, an upper bent edge and a lower bent edge. The through holes on the fins are aligned with one another. The upper and the lower bent edges are respectively provided with at least one fastening section. The fins are sequentially fastened to one another through connection of the fastening sections on one fin to the fastening sections on another adjacent fin to thereby form a heat sink having fins or a heat dissipation fin assembly, and all the upper bent edges and the lower bent edges of the fins together constitute a top surface and a bottom surface, respectively, of the heat sink or the heat dissipation fin assembly.

Further, each of the through holes on the fins is provided with a flange, which is projected from one side to another opposite side of the fin. The heat pipe has a first end that extends through the through holes and is surrounded by the flanges. A second end of the heat pipe extends through the bottom surface of the heat sink or the heat dissipation fin assembly or through a base thereof.

Generally, the through holes on the fins and the first end of the heat pipe are connected to one another mostly by tight fit or loose fit. In the case of tight fit, the flanges of the through holes respectively have an inner diameter slightly smaller than an outer diameter of the first end of the heat pipe, so that an interference fit is formed between the flanges and the first end of the heat pipe. Alternatively, according to the principle of thermal expansion, the fins can be heated to expand the inner surfaces of the flanges and then let them cool after the heat pipe is fully extended through the through holes. At this point, the inner diameter of the cooled flanged is naturally reduced to its original size for the flanges to tightly fit around the heat pipe.

On the other hand, in the case of loose fit, the flange has an inner diameter slightly larger than an outer diameter of the first end of the heat pipe and a medium, such as a thermal glue, a thermal paste, or a tin solder rod, is provided between the through holes on the fins and the heat pipe for gap filling. One of the ways to set the medium is to place it between inner surfaces of the flanges of the through holes and the outer surface of the first end of the heat pipe. Another way is to form a filler hole at an edge of the through holes for receiving the medium therein. In the process of fabrication, the medium is heated to melt and evenly distribute between the outer surface of the heat pipe and the inner surfaces of the flanges of through holes.

The tight fit can also be realized by providing a corrugated structure around the flanges by compressing the flanges with a tightening device. The corrugated structure includes a plurality of protrusions and dents, which are continuously and alternately arrayed along a circumferential surface of the flanges to apply a radially inward force on the heat pipe, causing the outer surface of the heat pipe to deform, so that interference fit is formed between the deformed outer surface of the heat pipe and the flanges with the corrugated structure, enabling the flanges and the heat pipe to tightly connect to one another.

In consideration of the requirements for reduced overall weight and manufacturing cost of heat sink, aluminum material having light weight and low cost is usually selected for forming the fins, the heat sink, and the base of the heat sink, while other metal materials with high thermal conductivity, such as brass, aluminum, nickel and stainless steel, are selected for forming the heat pipe.

While the use of aluminum material in replace of copper material indeed improves the problems of heavy overall weight and high manufacturing cost, it brings other problems at the same time. First, the aluminum surface tends to oxidize easily and will produce oxide during the welding process. The produced oxide has a high melting point, which hinders the welding metal from being molten fully and brings difficulties to the welding operation. When welding copper material to aluminum material, one side of the weld joint located closer to the copper material tends to form copper aluminide (CuAl₂) eutectic, which is distributed in the vicinity of grain boundaries to easily cause the problem of fatigue crack propagation through grain boundaries. Besides, copper and aluminum materials are quite different in their melting points and eutectic temperatures. When the surface of the aluminum has fully molten in the welding operation, the copper is still in a solid phase. On the other hand, when the copper is molten, the aluminum has long been molten and could not co-exist with the molten copper in the eutectic state to further increase the difficulty of welding operation. Further, since the copper material and the aluminum material all have good heat conductivity, the metal in the weld pool crystallizes quickly, which prevents the reaction gas used in pyrometallurgy from timely escaping from the weld pool to form air pores in the weld joint easily. Therefore, the copper material and the aluminum material could not be directly welded together. The surface of the aluminum material must be modified to enable subsequent welding of the aluminum material to the copper material or other metal materials.

To overcome the problem that the aluminum material used in place of the copper material could not be directly welded to other members of the heat sink assembly made of the copper material and other dissimilar metal materials, electroless nickel plating is one of the technical means adopted for aluminum surface modification. Generally, electroless nickel plating can be classified into three types, namely, low, middle and high phosphorus electroless nickel plating. The electroless nickel plating is particularly different from the electroplating in that it is performed in a working environment without electric current and uses reducing agent in the plating solution to reduce metal ions. Prior to the electroless nickel plating, a specimen surface must be catalyzed. There are three types of electroless nickel plating solution. The first type contains activator, sensitizer, and an acidic plating bath having a pH value between 4 and 6, and is characterized in that less loss in chemical composition is caused by evaporation; this type of electroless nickel plating solution requires a relatively higher operating temperature, but is considerably safe for use and easy to control; and it has high phosphorus content and high plating rate and is often used in the industrial field. The second type contains activator, sensitizer, and a basic plating solution or bath having a pH value between 8 and 10. Since the ammonia solution used to adjust the pH value of the plating bath is volatile, it must be replenished timely to maintain stable pH value of the plating bath; this type of electroless nickel plating solution has less phosphorus content, is less stable and needs only a lower operating temperature. (3) The third type contains HPM and a basic plating solution. HPM means a mixture of hydrochloric acid and peroxide. When a silicon chip is immersed in a mixture of deionized (DI) water, hydrogen peroxide (H₂O₂) and hydrogen Chloride (HCl) in a mixing ratio of 4:1:1, the oxide layer formed on the surface of the silicon chip can replace the sensitizer and the activator to form an autocatalytic surface.

Electroless nickel plating requires a large quantity of chemical reaction liquid during the process and produces a large quantity of industrial liquid waste containing heavy metals or chemical substances after the process. Industrial liquid waste generates a large amount of wastewater that contains toxicants, such as yellow phosphorus. In the case of yellow phosphorus-containing wastewater, the concentration of yellow phosphorus thereof reaches 50~390 mg/L. Yellow phosphorus is highly toxic, and its existence in human body would badly endanger liver and other organs. Drinking phosphorus-containing water for a long time would result in osteoporosis to cause different diseases, such as mandible necrosis. Currently, many countries in the world have forbidden the use of electroless nickel plating and actively promote non-toxic chemical processes to ensure environmental protection.

In view of the above facts, it is very important to work out a way to reduce an overall structural weight of the conventional heat dissipation module, and to use other surface modification process instead of electroless nickel plating to improve the welding of aluminum fins to other members of the heat sink assembly made of dissimilar metal materials without producing environmental pollutants.

It is therefore tried by the inventor to develop an improved heat sink assembly with heat pipe to overcome the disadvantages in the prior art.

SUMMARY OF THE INVENTION

To improve the above-mentioned problems, a primary object of the present invention is to provide a heat sink assembly with heat pipe, which includes a copper embedding layer formed on areas of an aluminum fin assembly that are to be connected to other members of the heat sink assembly made of a metal material different from aluminum, such as copper heat pipes, so that the aluminum fin assembly and the copper heat pipes made of dissimilar metal materials can be directly welded to one another without the need of first performing an electroless nickel plating on the aluminum fin assembly. In this manner, no toxic substance would be produced and can therefore ensure environmental protection; and the problem of eutectic as found in the prior art can be improved.

Another object of the present invention is to provide a heat sink assembly with heat pipe including an aluminum fin assembly, areas on which for connecting to a copper heat pipe and/or a copper base are respectively provided with a copper embedding layer, so that the aluminum fin assembly can be directly welded to the copper heat pipe or the copper base via the copper embedding layer without the need of electroless nickel plating. In this manner, it is able to reduce an overall weight of the heat sink assembly and to reduce thermal resistance at connecting joints between the aluminum fin assembly and the copper heat pipe and/or the copper base while upgrade the heat transfer efficiency of the heat sink assembly.

To achieve the above and other objects, the present invention provides a heat sink assembly with heat pipe, which includes at least one aluminum fin assembly and at least one copper heat pipe. The aluminum fin assembly includes a plurality of aluminum fins sequentially fastened to one another, and has a bottom surface and a top surface. Any two adjacent aluminum fins together define a flow passage between them. The bottom surface is provided with at least one groove, which has an open side and a groove inner surface. The aluminum fins are respectively provided with a through hole that extends through the aluminum fin in a thickness direction thereof, and the through holes respectively include a flange, which is projected from one side of the aluminum fin. The groove inner surface is an area of the aluminum fin assembly for connecting to the copper heat pipe and is provided with a copper embedding layer, which includes a deepening surface and a connecting surface. The deepening surface bonds to and deeply penetrates into the groove inner surface. The at least one copper heat pipe has a first end and a second end extended through the through holes and the groove on the aluminum fin assembly, respectively. The first end is connected to the through holes and the flanges by tight fit, and the second end is in contact with and connected to the connecting surface of the copper embedding layer provided on the groove inner surface.

The second end of the at least one copper heat pipe has an exposed surface exposed from the open side of the groove; and a contact surface in contact with the connecting surface of the copper embedding layer on the groove inner surface and is connected thereto by welding.

The flange of every through hole has a corrugated or notched structure formed around it for tightly binding to an outer surface of the first end of the copper heat pipe.

The bottom surface is another area of the aluminum fin assembly to be connected to other members of the heat sink assembly and has the copper embedding layer provided thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings, wherein

FIGS. 1A and 1B are exploded and assembled bottom perspective views, respectively, of a heat sink assembly with heat pipe according to a preferred embodiment of the present invention;

FIG. 1C is an assembled top perspective view of the heat sink assembly with heat pipe according to the preferred embodiment of the present invention;

FIG. 1D shows an outermost fin of an aluminum fin assembly included in the present invention is turned inside out to connect to other fins;

FIG. 2A is a sectional view of the aluminum fin assembly in the present invention;

FIG. 2B is a sectional view showing the connecting of the aluminum fin assembly with a copper heat pipe; and

FIGS. 3A and 3B show the aluminum fin assembly before and after being provided with a copper embedding layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described with some preferred embodiments thereof and the accompanying drawings.

Please refer to the accompanying drawings; wherein FIGS. 1A and 1B are exploded and assembled bottom perspective views, respectively, of a heat sink assembly with heat pipe according to the present invention, FIG. 1C is an assembled top perspective view of the present invention, FIG. 1D shows an outermost fin of an aluminum fin assembly included in the present invention is turned inside out to connect to other fins, FIG. 2A is a sectional view of the aluminum fin assembly in the present invention, and FIG. 2B is a sectional view showing the connecting the aluminum fin assembly with a copper heat pipe. As shown, the heat sink assembly is a heat sink structure 10 including an aluminum fin assembly 11 and at least one copper heat pipe 121. The aluminum fin assembly 11 has a bottom surface 113 and a top surface 116. On the bottom surface 113, there is provided at least one groove 115. In the illustrated preferred embodiment, two grooves 115 are shown. Every groove 115 has an open side 1151 located flush with the bottom surface 113 and a groove inner surface 1152 recessed from the bottom surface 113. The bottom surface 113 and the groove inner surfaces 1152 are areas on the aluminum fin assembly 11 to be connected to other copper parts as will be described in detail later.

The aluminum fin assembly 11 is formed of a plurality of fins 111 sequentially fastened to one another in a horizontal direction or a vertical direction, and any two adjacent fins 111 define a flow passage 117 between them. The fins 111 are made of aluminum or an aluminum alloy. In the illustrated preferred embodiment, every aluminum fin 111 has an upper bent edge 1111 and a lower bent edge 1112, which are projected from one side of the aluminum fin 111 to align with the upper bent edge 1111 and the lower bent edge 1112 of another adjacent aluminum fin 111. The upper bent edge 1111 and the lower bent edge 1112 are respectively provided with at least one fastening section 11111, 11121. In the illustrated preferred embodiment, the fastening sections 11111, 11121 are snap-fit structures. However, it is understood the illustration is non-restrictive and other known technical means for fastening may also be adopted. The aluminum fins 111 are sequentially horizontally connected to one another by snap fitting the fastening sections 11111, 11121 of one aluminum fin 111 to the fastening sections 11111, 11121 on another adjacent aluminum fin 111 to thereby form a heat sink structure with snap-fitted fins.

With the above arrangements, the upper bent edges 1111 together form the top surface 116 of the aluminum fin assembly 11, and the lower bent edges 1112 together form the bottom surface 113 of the aluminum fin assembly 11. Further, the lower bent edge 1112 of every aluminum fin 111 is provided with at least one downward opened recess. When the aluminum fins 111 are sequentially fastened together, the downward opened recesses are aligned with one another to constitute the groove 115 on the bottom surface 113. Further, the aluminum fins 111 are respectively provided with at least one through hole 114, which extend through the aluminum fin 111 in a thickness direction thereof and are aligned with one another. Every through hole 114 has a flange 1141 formed around a rim thereof and projected from one side of the aluminum fin 111. In the illustrated preferred embodiment, the flanges 1141 are projected from a front side of the aluminum fins 111. The flanges 1141 respectively define a flange inner surface 1143. In practical implementation of the present invention, the aluminum fin assembly 11 may be otherwise formed by sequentially vertically fastening the aluminum fins 111 to one another. As can be seen in FIG. 1D, an outermost aluminum fin 111 of the aluminum fin assembly 11 is turned inside out when being connected to an adjacent aluminum fin 111, so that no upper bent edge 1111 and lower bent edge 1112 would expose to outside and undesirably scratch other members of the heat sink assembly.

In the illustrated preferred embodiment, there are shown two copper heat pipes 121, which can be U-shaped heat pipes, for example, and made of copper or a copper alloy. The copper heat pipes 121 can be, for example, round, D-shaped or flat in cross section. Each of the copper heat pipes 121 includes a first end 1211 and a second end 1212. The first ends 1211 are extended through the through holes 114 and connected to the flanges 1141 through tight fit. For example, the flange inner surfaces 1143 of the flanges 1141 respectively have an inner diameter slightly smaller than an outer diameter of the first ends 1211 of the copper heat pipes 121, so that an interference fit is formed between the flanges 1141 and the first ends 1211 of the copper heat pipes 121. Or, according to the principle of thermal expansion, the aluminum fins 111 can be heated to expand the inner diameter of the flanges 1141 and then let the fins 111 cool after the copper heat pipes 121 are fully extended through the through holes 114. At this point, the inner diameter of the cooled flanges 1141 is naturally reduced to its original size to form a tight fit between the flanges 1141 and the copper heat pipes 121. The second ends 1212 are extended to the bottom surface 113 of the aluminum fin assembly 11 and through the grooves 115. As can be seen in FIG. 1A, the second ends 1212 of the copper heat pipes 121 respectively have an exposed surface 12121 corresponding to the open side 1151 of the groove 115 and a contact surface 12122 facing toward the groove inner surface 1152.

In the illustrated present invention, every copper heat pipe 121 has a U-shaped section 1213 formed between the first end 1211 and the second end 1212 to extend from the first end 1211 to the second end 1212. The first end 1211 and the second end 1212 of each copper heat pipe 121 serve as a condensation end and an evaporation end, respectively. The copper heat pipe 121 also has at least one wick structure and a working fluid provided therein. The at least one wick structure may be, for example, a plurality of grooves, a powder sintered structure, a mesh structure, a fibrous structure, a corrugated plate, or any combination thereof extended in the copper heat pipe 121 from the first end 1211 to the second end 1212.

In the copper heat pipe 121 illustrated in the preferred embodiment, the first end 1211 is round in cross section while the second end 1212 is D-shaped or flat in cross section. That is, the exposed surface of the second end 1212 is a flat surface formed by, for example, pressing with a tool or milling with a milling cutter and is located flush with the bottom surface 113 of the aluminum fin assembly 11. However, the above illustration is non-restrictive. In other alternative embodiments, the first end 1211 and the second end 1212 can be the same in cross section, such as a round or a flat cross section.

In an alternative embodiment, the flange 1141 on every aluminum fin 111 has a corrugated or notched structure formed around it for forming an interference fit between an outer surface of the first end 1211 of the copper heat pipe 121 and the flange 1141. More specifically, after the first end 1211 of the copper heat pipe 121 is extended through the through hole 114, the flange 1141 is compressed with a tightening device to form the corrugated or notched structure. The corrugated or notched structure includes a plurality of protrusions and dents, which are continuously and alternately arrayed along a circumferential surface of the flange 1141 to apply a radially inward force on the copper heat pipe 121, causing an outer surface of the latter to deform. Further, interference fit is formed between the deformed outer surface of the copper heat pipe 121 and the flange 1141 with the corrugated or notched structure. In this manner, the first end 1211 of the copper heat pipe 121 is fixedly held to the aluminum fins 111 without the risk of separating from the through holes 114.

FIGS. 3A and 3B show the aluminum fin assembly 11 before and after being provided with a copper embedding layer 14. Please refer to FIGS. 3A and 3B along with FIGS. 1A, 1B, 2A and 2B. A copper embedding layer 14 is provided at areas of the aluminum fin assembly 11 corresponding to the groove inner surfaces 1152 and the bottom surface 113, at where the aluminum fin assembly 11 is to be connected to other members of the heat sink assembly. The copper embedding layer 14 includes a deepening surface 141 and a connecting surface 142, which are located at two opposite sides of the copper embedding layer 14. The deepening surface 141 bonds or grips to, is embedded or buried in, or is deposited on the groove inner surfaces 1152 and the bottom surface 113; and the connecting surface 142 is an exposed surface of the copper embedding layer 14 for contacting with and connecting to other members of the heat sink assembly. In some operable embodiments, the copper embedding layer 14 can be copper sheet, copper foil, copper powder/granules, or liquid copper applied to the groove inner surfaces 1152 and the bottom surface 113 through mechanical processing, such as pneumatic pressing, hydraulic pressing, stamping, oil pressing, extruding or hammering; or through surface finishing, such as spraying, electroplating or printing; or through chemical processing, such as electroplating or anodizing. In the course of forming the copper embedding layer 14, a part of the copper embedding layer 14 directly grips to, is embedded or buried in, deeply penetrates into, or is deposited on the groove inner surfaces 1152 and the bottom surface 113 to form the deepening surface 141 of the copper embedding layer 14.

Therefore, the copper embedding layer 14 is not only connected at the connecting surface 142 to the groove inner surfaces 1152 and the bottom surface 113, but also has the deepening surface 141 gripped to, embedded or buried in, or deposited on the groove inner surfaces 1152 and the bottom surface 113 to form a foundation of the copper embedding layer 14, which increases the binding strength between the copper embedding layer 14 and the groove inner surfaces 1152 and the bottom surface 113 and prevent the copper embedding layer 14 from peeling off or separating from the groove inner surfaces 1152 and the bottom surface 113.

With the above arrangements, the grooves 115 on the aluminum fin assembly 11 can be connected to the contact surfaces 12122 of the second ends 1212 of the copper heat pipes 121 via the connecting surface 142 of the copper embedding layer 14 on the groove inner surfaces 1152. More specifically, for example, solder can be used between the connecting surface 142 of the copper embedding layer 14 and the contact surfaces 12122 of the copper heat pipes 121 to weld them to one another. Alternatively, the connecting surface 142 of the copper embedding layer 14 and the contact surfaces 12122 of the copper heat pipes 121 can be connected together by supersonic welding or laser welding. Thus, the aluminum fin assembly 11 can be directly welded to the copper heat pipes 121 made of a dissimilar metal material without the need of electroless nickel plating.

In the present invention, the bottom surface 113 of the aluminum fin assembly 11 may be optionally connected to a heat conducting base made of a copper-based material, such as pure copper or any copper alloy. The heat conducting base can be a solid base plate or a hollow vapor chamber internally provided with a working fluid. The bottom surface 113 can be connected, such as by welding, to the copper-based heat conducting base via the connecting surface 142 of the copper embedding layer 14, while the exposed surfaces at the second ends 1212 of the copper heat pipes 121 can also be directly connected, such as by welding, to the copper-based heat conducting base. With the copper embedding layer 14, the aluminum fin assembly 11 can be directly welded to the copper-based heat conducting base made of a dissimilar metal material without the need of electroless nickel plating. Thus, no toxic substances would be produced in the manufacturing process of the heat sink structure 10 to ensure good environmental protection and the problem of forming eutectic as found in the prior art is also improved.

In the illustrated preferred embodiment, the two copper heat pipes 121 are extended from the same side into the aluminum fin assembly 11. However, it is understood the illustration is non-restrictive. In other alternatively embodiments, the heat sink structure 10 can include a plurality of copper heat pipes 121 and the aluminum fin assembly 11 is formed with through holes and grooves 115 respectively in a number the same as the copper heat pipes 121; and the copper heat pipes 121 can be arranged at staggered or non-staggered locations and extended into the aluminum fin assembly 11 from two opposite sides thereof to upgrade the heat dissipation efficiency of the heat sink structure 10.

The present invention has been described with some preferred embodiments thereof and it is understood that many changes and modifications in the described embodiments can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims. 

What is claimed is:
 1. A heat sink assembly with heat pipe, comprising: at least one aluminum fin assembly being formed of a plurality of aluminum fins sequentially fastened to one another, and having a bottom surface and a top surface; any two adjacent ones of the aluminum fins defining a flow passage between them; the bottom surface being provided with at least one groove, which has an open side and a groove inner surface; the aluminum fins being respectively provided with a through hole that extends through the aluminum fin in a thickness direction thereof, and the through holes respectively including a flange, which is projected from one side of the aluminum fin; the groove inner surface being an area of the aluminum fin assembly for connecting to other members of the heat sink assembly and being provided with a copper embedding layer thereon, which includes a deepening surface and a connecting surface; and the deepening surface bonding to and deeply penetrating into the groove inner surface; and at least one copper heat pipe having a first end and a second end extended through the through holes and the groove on the aluminum fin assembly, respectively; and the first end being connected to the flanges by tight fit, and the second end being in contact with and connected to the connecting surface of the copper embedding layer provided on the groove inner surface.
 2. The heat sink assembly with heat pipe as claimed in claim 1, wherein the second end of the at least one copper heat pipe has an exposed surface and a contact surface; and the exposed surface being exposed from the groove while the contact surface being in contact with and connected to the connecting surface of the copper embedding layer provided on the groove inner surface. 